1. Field of the Invention
This invention relates to an illumination and exposure system for a reproduction apparatus and method and more particularly to an improvement in the synchronizing of the exposure of a photosensitive member used in such apparatus and method.
2. Brief Description of the Prior Art
Modern high speed electrostatic type copiers or reproduction machines may use flash lamps to illuminate, i.e. expose, the original being copied. Use of this type of lamp is one way of providing the necessary exposure speed for very high speed copying. In these arrangements, the entire original is illuminated by the flash lamps providing what is known to the art as full frame exposure.
Since the originals to be copied may be relatively large, and the entire area must be illuminated fully, flash lamps must generate intense light energy over the span of a few microseconds. To support such illumination intensity in turn requires a very large amount of electrical energy with an attendant large, expensive, capacitance type power supply.
To reduce the intensity of illumination required to be provided by the lamps, it has been proposed to extend the period of illumination of the lamps. Inasmuch as the photosensitive member being exposed is moving during this period while the document is stationary, it has been further proposed to move an optical member so that the image of the original moves with the photosensitive member so as to reduce image smear, see U.S. Pat. No. 4,111,541 to Townsend.
After an electrostatic latent image of the original is formed, it is developed and transferred in register to a copy sheet or other support. In a reproduction apparatus wherein a multicolor reproduction of the original is to be made, the original may be flash exposed through color separation filters onto several separate image frames on a photosensitive web, the frames developed with respective colored toners and the developed images serially transferred in register onto a copy sheet or support. Obviously, registration of the separate colored images on the support is of importance in producing of such reproductions.
A means of registration of images on a photoconductor with transfer to a copy sheet has been described in U.S. Pat. No. 4,477,176 to Russel, wherein a roller is used to retain a copy sheet and move same into transfer relationship with several image frames on the photosensitive member. Timing of this roller is controlled by a logic and control unit which in turn receives timing signals regarding web movement from a timing signal generator that senses regularly spaced perforations on the web.
As indicated in U.S. Pat. No. 4,025,186 to Hunt, Jr. et al, a photosensitive web may be provided with two types of perforations, one comprising a series of closely spaced perforations for providing timing signals and the other identifying frame locations on the web for use in triggering a flash exposure. Where an optical element is to be moved during an exposure, it is desirable to synchronize lens movement with the web and provide triggering of the flash unit in accordance with lens position and web position or for example copy sheet registration, see U.S. Pat. No. 3,995,950 which describes a complex system for timing of flash triggering.
It is an object of this invention to provide a full frame exposure system for electrostatic type reproduction apparatus and methods with simplified and improved means for timing exposure of a photosensitive member with an imaging optical member that is moving.